Most Common Fuel Supply System in Petrol Engine

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What is the fuel supply system in the petrol engine?

In the petrol engine, the fuel supply system is made up of a fuel tank, pump, filter, injectors or carburetor, and is responsible for delivering the fuel to the engine as needed.

Each component must perform seamlessly to achieve the expected performance and reliability.

Petrol from the fuel tank has to be filled into a carburetor so that it can be mixed with air for onward feeding to the cylinder. fuel is fed to the carburetor in two ways namely:

  • Gravity feed system
  • Forced feed system

(A) Gravity feed system

In this fuel supply system in the petrol engine, the fuel tank is placed above the level of the carburetor and is connected to it with the help of pipe fuel flows to the carburetor due to its own gravity.

Such a system is not used in a motor vehicle as there is no place to keep the tank at a higher level however this system is used in almost all the motorcycle and scooters being it very cheap.

(B) Forced feed system

In this fuel supply system in the petrol engine, the tank is placed at a distance and also under the level of the carburetor to pump the fuel from low level and feed it to the carburetor fuel pump is used. In almost all the vehicle this system is used.

components are attached to the fuel supply system in the petrol engine.

The main part of the fuel feed system is employed in a motor vehicle are shown below:

  • Fuel tank
  • Fuel pump
  • Fuel filter

now let us discuss the construction and working of these units.

● Fuel tank

It is made of galvanized MS sheet and is fast and under the chassis with straps nuts and bolts with rubber packing in between.

Petrol connection is taken at the bottom sometimes a fine wire gauge strainer is also fitted in it so that petrol leaving the tank is free from coarse suspended impurities.

The drain plug is fitted at the lowest portion of the tank sometimes plug position of the tank is dished so that condenser water being heavier than petrol can settle here.

In a rainy season, this condensed water should be drained by opening the drain plug at regular intervals the fuel tank has 2/3 compartments interconnected with each other.

This compartment are made in the bank so that fuel does not strike with walls of the tank when the vehicle is moving on rough road.

Fueltank has a neck made on its top where tank cap is placed on the neck a small air bleed pipe is also welded so that when fuel is being consumed by the engine space vacated by the fuel is fill up by air.

In some of the vehicle instead of providing an air bleed pipe in air bleed hole is drilled in the cap itself.

● Fuel filter

In some of the fuelpumps trainer is placed in the glass bowl it requires cleaning at each service.

Automobile fuel filter

In some of the vehicle a separate fuelfilter is connected between carburettor and fuelpump this glass bowl and the filter element should be cleaned and each service.

While in some other makes inline type of filter this type of filter is not cleanable and has to be replace when found dirty.

Fuelfilter fitted to Maruti engine is not cleanable type hence complete assembly has to be changed at 40,000 kilometre.

While fitting the filter and sure that outlet coming on top and inlet is at the lower end of body.

● Fuel pump

The function of fuelpump is to pump fuel from the tank and feed it to the carburettor.

These pump are designed to pump sufficient quantity of fuel at all working condition so that the pipeline always remains filled up with fuel at all working condition failing which these are chances of paper Lok usually called airlock in the pipeline

There are two types of pump used these are :

(B) Electrical fuel pump.

(A) Mechanical fuel pump

Electric fuel pump

In some of the vehicles instead of mechanical fuelpump electrical fuel pump is fitted which is connected through ignition key there are two types of pump available these are :

(A ) Stomach siphon (Diaphragm type)

Diaphragm type Electric fuel pump

A stomach siphon (otherwise called a Membrane siphon) is a positive removal siphon that utilizes a mix of the responding activity of an elastic, thermoplastic or teflon stomach and appropriate valves on either side of the stomach (check valve, butterfly valves, fold valves, or some other type of shut-off valves) to siphon a liquid.

At the point when the volume of an office of either kind of siphon is expanded (the stomach climbing), the weight diminishes, and liquid is brought into the chamber.

At the point when the chamber pressure later increments from diminished volume (the stomach descending), the liquid recently attracted is constrained out.

At long last, the stomach climbing by and by brings liquid into the chamber, finishing the cycle. This activity is like that of the chamber in an inner ignition motor.

Stomach Pumps convey an airtight seal between the drive component and the pressure chamber, permitting the siphon to move, pack, and empty the medium without an oil.

An elastomeric stomach can be utilized as an adaptable unique seal that expels a large number of the confinements found with other fixing strategies.

They don’t release, offer little grinding, and can be built for low weight affectability.

With the correct material thought, stomachs can seal over a wide scope of weights and temperatures without requiring grease or support.

(B) Bellow type

In this siphon rather than stomach adaptable metal underneath is utilized the siphon work similarly as expressed for stomach type.


Insurances to be taken for the electric fuel siphon :

(1) don’t interface the battery in Reverse extremity.

(2) don’t drop the siphon.

(3) don’t have any significant bearing overvoltage.

(4) don’t introduce the siphon close to high temperature.

(5) make right electrical association on fuel siphon.

(6) never keep the terminal free.

(7) keep fuel line joint completely close and there ought to be no spillage.

Fuel pump troubleshooting

Note :- if your vehicles fuelpump supplies less fuel, so read carefully these table below.

Possible causesRemedies
blocked vent screw on fuel tank.Clean the vent hole.
choked or bent fuel pipe from tank to fuel pump or fuel pump to carburettor.Clean the pipe remove sharp bend or replace squeezed pipe.
loose petrol pipe connection.Tighten the unions.
Choked petrol strainer in fuel pump or tank. Clean the strainer.
loose filter housing on fuel pump.Tighten it fully.
broken or pressed filter housing packaging.Replace with new one.
leaky diaphragm.Replace diaphragm.
Valve holding clip loose.Tighten it fully.
leaky valve.reface if split valve otherwise change.
rocker arm pin moved out of its place or worn out pin.Reposition the pin and lock it;if worn out replace.
worn out rocker arm.rebuild or replace.
loose body screwTighten it fully.
thick gasket used for mounting fuel pump to block.use thinner gasket

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